Algorithm for determining the capacity of a battery while in service

A method for estimating a capacity of a high voltage vehicle battery in a vehicle, said method comprising:

• providing, in a processor, battery data including a previous battery state-of-charge for a previous drive cycle of the vehicle, an integrated battery current amp-hours for the previous drive cycle of the vehicle, battery voltage and battery temperature;
• determining, in the processor, that battery contactors have been closed after the contactors have been opened to disconnect the battery from a high voltage vehicle bus;
• determining, in the processor, if the battery has been at rest for a long enough period of time while the contactors were open where the rest time is based on battery temperature;
• determining, in the processor, an initial battery voltage as a battery voltage from a last time step when the battery contactors were closed prior to the contactors being opened during the battery rest time;
• determining, in the processor, a present battery state-of-charge from the initial battery voltage and the battery temperature;
• determining, in the processor, whether the present battery state-of-charge is a valid state-of-charge;
• and
• calculating, in the processor, the battery capacity based on the integrated battery current amp-hours divided by the difference between the present battery state-of-charge and previous battery state-of-charge if the present battery state-of-charge is valid.

A system for estimating capacity of a battery, said system comprising:

• means for providing battery data including a previous battery state-of-charge, battery voltage, battery temperature and integrated battery current amp-hours;
• means for determining that battery contactors have been closed after the contactors have been opened to disconnect the battery from a load;
• means for determining if the battery has been at rest for a long enough period of time while the contactors were open where the battery rest time is based on battery temperature;
• means for determining an initial battery voltage as a battery voltage from a last time step when the battery contactors were closed prior to the contactors being opened during the battery rest time;
• means for determining a present battery state-of-charge from the initial battery voltage and the battery temperature;
• and
• means for calculating the battery capacity based on the integrated battery current amp-hours divided by the difference between the present battery state-of-charge and the previous battery state-of-charge.